Speaker
Description
The electron pressure profile is a convenient tool to characterize the thermodynamical state of a galaxy cluster, with several studies adopting a "universal" functional form. In this talk, I will present a recent work aimed at testing this assumption over a population-level cluster sample, using Sunyaev-Zel'dovich (SZ) data and four different parameterizations for the cluster pressure profile: generalized Navarro-Frenk-White (gNFW), $\beta$-model, polytropic, and exponential.
A set of 3496 ACT-DR4 galaxy clusters, spanning the mass range $[10^{14},10^{15.1}]\,\text{M}_{\odot}$ and the redshift range [0,2] , was stacked on the ACT-DR6 Compton parameter $y$ map over $\sim 13,000\,\text{deg}^2$ . An angular Compton profile was then extracted and modeled using the theoretical pressure recipes, whose free parameters were constrained against the measurement via a multi-stage MCMC approach. The analysis was repeated over cluster subsamples spanning smaller mass and redshift ranges. All functional forms were effective in reproducing the measured $y$ profiles within their error bars, without a clearly favored model. While best-fit estimates were in broad agreement with previous findings, hints of residual subsample dependency were detected favoring higher amplitudes and steeper profiles in high-mass, low-redshift clusters.
This work shows that population-level cluster studies based on SZ data alone are likely unable to accurately constrain different pressure profile models. Residual trends at population level and scatter at individual cluster level undermine the universal pressure model assumption whenever high precision is required. Finally, functional forms different from the gNFW proved equally effective while being more physically motivated.
| Research Area | Cosmology: late universe |
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